1. Technical Field
The present disclosure relates to a decoding circuit and, more particularly, to a decoding circuit and method for improving error correction capability in a terrestrial digital multimedia broadcasting (T-DMB) system, and a recording medium for recording the method.
2. Discussion of the Related Art
A T-DMB system is a standard for broadcasting systems providing multimedia broadcasting services including high-quality audio, video and data services. The T-DMB system uses Moving Picture Experts Group standard-4 (MPEG-4) Advanced Video Coding (AVC) and MPEG-4 Bit Sliced Arithmetic Coding (BSAC) to provide high-quality audio, video or data signals at a low bandwidth of less than 512 kbps.
FIG. 1 illustrates a block diagram of a conventional T-DMB system. Referring to FIG. 1, the conventional T-DMB system 10 includes a transmission unit 20, a channel 30, and a receiving unit 40. The transmission unit 20 includes an MPEG-4 encoder 21, a multiplexer 23, a Reed-Solomon (RS) encoder 25, an interleaver 27, a convolutional encoder 28, and a modulator 29.
The MPEG-4 encoder 21 codes a source signal, for example, a video signal, an audio signal, or a data signal at high efficiency and packetizes the encoded source signal, for example, a video stream, an audio stream, or a data stream. The multiplexer 23 encapsulates streams packetized by the MPEG-4 encoder 21 in a standard. MPEG transport stream.
The RS encoder 25 codes the standard MPEG transport stream output from the multiplexer 23. In other words, the RS encoder 25 converts the standard MPEG transport stream into an RS code. The interleaver 27 interleaves the coded standard MPEG transport stream output from the RS encoder 25.
The convolutional encoder 28 performs trellis coding of the interleaved standard MPEG transport stream. The modulator 29 modulates, for example, performs orthogonal frequency division multiplexing (OFDM) modulation of, the trellis coded standard MPEG transport stream output from the convolutional encoder 28 and transmits the modulated standard MPEG transport stream to the receiving unit 40 via the channel 30.
The receiving unit 40 includes a demodulator 41, a Viterbi decoder 43, a deinterleaver 45, an RS decoder 47, a demultiplexer 48, and an MPEG-4 decoder 49.
The demodulator 41 demodulates a signal Dq received via the channel 30. The Viterbi decoder 43 decodes the demodulated signal output from the demodulator 41. The deinterleaver 45 deinterleaves the decoded signal output from the Viterbi decoder 43. The RS decoder 47 decodes a deinterleaved signal Dp output from the deinterleaver 45 and outputs a decoded signal Dq.
The demultiplexer 48 divides the decoded signal Dq output from the RS decoder 47 into a video stream, an audio stream, and a data stream. The MPEG-4 decoder 49 performs MPEG decoding of the streams, for example, a video stream, an audio stream, and a data stream, output from the demultiplexer 48.
FIG. 2 illustrates a conventional RS codeword. Referring to FIGS. 1 and 2, the RS codeword includes data 210 and a parity byte 220. The RS codeword is “n” bytes in length. The data 210 is “k” bytes in length and the parity byte 220 is 2 t (=n−k) bytes in length. When a RS codeword output from the RS encoder 25 is the same as the RS codeword illustrated in FIG. 2, the RS decoder 47 can correct “t” error bytes existing in the RS codeword. Here, “n”, “k”, and “t” are natural numbers.
For example, the RS decoder 47 can correct a maximum of 8 byte errors with respect to a RS codeword (e.g., n=204, k=188, t=8). Here, the RS decoder 47 has an error correction capability of 8 bytes.
When errors detected by the RS decoder 47 exceed the error correction capability, for example, 8 bytes, however, the RS decoder 47 fails in error correction. When the RS decoder 47 fails in error correction, the demultiplexer 48 will not demultiplex the RS codeword.
An encoded MPEG transport stream output from the RS encoder 25 includes at least one stuffing byte. In the T-DMB system 10, about 20 to 25 percent of all MPEG packets in a transport stream may include continuous stuffing bytes. These stuffing bytes are redundant information, needed to align a variable-rate stream produced by the RS encoder with the constant 25 throughput provided by the communication link. Usually, a stuffing byte value has a hexadecimal format of 0x0FF. Here, a section in which the stuffing bytes exist in an MPEG packet is referred to as the “stuffing byte section”.
FIG. 3A illustrates an example of an MPEG packet that does not include stuffing bytes. FIGS. 3B and 3C illustrate examples of MPEG packets including stuffing bytes. With respect to a source like fast-moving video having a large amount of information, an MPEG packet does not include stuffing bytes, as illustrated in FIG. 3A.
With respect to a source like slow-moving video having a small amount of information, however, an MPEG packet includes at least one stuffing byte, as illustrated in FIGS. 3B and 3C. In FIGS. 3A through 3C, the horizontal axis is a byte index and the vertical axis is a byte value. The amount of stuffing bytes in packets of a transport stream is inversely proportional to the amount of information in a source in a T-DMB system.
The MPEG transport stream including MPEG packets having stuffing bytes is converted into an RS codeword by the RS encoder 25. When the number of errors existing in the RS codeword exceeds the error correction capability of the RS decoder 47, the RS decoder 47 fails in error correction. Here, these errors include errors occurring in the stuffing byte section.
Information (or data) included in the stuffing byte section is not real information (or data) but is redundant information (or data). Accordingly, the errors occurring in the stuffing byte section are not real errors. Nonetheless, as a result, the error correction capability of the RS decoder 47 is reduced.